206 PHYTOPHTHORA PARASITICA. 



ment with hydrochloric acid, cupric ammonium hydrate dissolves 

 them completely in a short time. Thus the reactions which helped 

 Mangin to trace the presence of callose, pure or associated with 

 cellulose, in the Peronosporacece examined by him, have shown us 

 the complete absence of the substance from the plugs found in 

 Ph. parasitica. These plugs give all the colour and chemical 

 reactions for cellulose. Mangin has not only found callose plugs in 

 the mycelium of the Peronosporacew, but also callose depositions on 

 the walls. These depositions as well have been given great 

 importance by him, as being an important distinguishing character- 

 istic of the order. The mycelium of Ph. parasitica has been 

 found studded on its inner walls with some deposit which gives all 

 the chemical and colour reactions of cellulose and none of callose. 

 These cellulose deposits are very beautifully seen if the mycelium 

 be first treated with a strong acid, such as phosphoric acid, for a 

 few hours and then treated for a very short time with a weak 

 solution of cupric ammonium hydrate and stained with phosphoric 

 iodide after being well washed with water. The mycelium takes 

 a beautiful blue colour and the studs on it a darker blue, without 

 any trace of yellow in them. This studded mycelium looks quite 

 similar to what is figured by Mangin. 1 This studded deposit of 

 cellulose has also been found in sporangia and " resting " conidia. 

 Mangin has observed no deposit on the sporangia of the Pero- 

 nosporacece examined by him, at least he makes no mention of 

 them in his various notes on this subject I have consulted. 

 Callose has been found to be absent even from the septa. The 

 beginning of the formation of the septum is seen as a hazy, ill- 

 defined, hyaline and slightly refractive line, running from one wall to 

 the other in the midst of a mass of protoplasm. When stained 

 with iodine and phosphoric acid the septum stands out clearly by 

 its faint blue colour in the yellow coloured protoplasm. This hazy 

 and ill-defined line, later on becomes sharply defined and stains deep 

 blue with iodine and phosphoric acid. Cellulose thickening then 



1 Mangin, L. Recherches sur les Peronosporees. Bull. Soc. d'Hist, Nat. d'Autun, 

 VIII, 1895, fig. 8, p. 88, and fig. 9, p. 90. 



